fix: Apply oneof last-value wins during decode (#2193)

dcodeIO · web-flow · commit cf35cdc23237 · 2026-04-28T19:33:39.000+02:00
diff --git a/src/decoder.js b/src/decoder.js
@@ -109,6 +109,8 @@ function decoder(mtype) {
                 : "%s=types[%i].decode(r,r.uint32(),undefined,n+1)", ref, i);
         else gen
                 ("%s=r.%s()", ref, type);
+        if (field.partOf) gen
+                ("m%s=%j", util.safeProp(field.partOf.name), field.name);
         gen
                 ("break")
             ("}");
diff --git a/tests/comp_oneof.js b/tests/comp_oneof.js
@@ -53,6 +53,11 @@ tape.test("oneofs", function(test) {
     test.equal(buf[0], 16, "should write id 1, wireType 0");
     test.equal(buf[1], 0, "should write a value of 0");
 
+    message = Message.decode([ 10, 1, 97, 16, 1 ]);
+    test.equal(message.kind, "num", "should decode the last value");
+    test.notOk(message.hasOwnProperty("str"), "should delete previous values while decoding");
+    test.same(Array.prototype.slice.call(Message.encode(message).finish()), [ 16, 1 ], "should re-encode only the last value");
+
     test.end();
 
 });
diff --git a/tests/data/test.js b/tests/data/test.js
@@ -7827,18 +7827,22 @@ $root.jspb = (function() {
                     switch (tag >>> 3) {
                     case 3: {
                             message.pone = reader.string();
+                            message.partialOneof = "pone";
                             break;
                         }
                     case 5: {
                             message.pthree = reader.string();
+                            message.partialOneof = "pthree";
                             break;
                         }
                     case 6: {
                             message.rone = $root.jspb.test.TestMessageWithOneof.decode(reader, reader.uint32(), undefined, long + 1);
+                            message.recursiveOneof = "rone";
                             break;
                         }
                     case 7: {
                             message.rtwo = reader.string();
+                            message.recursiveOneof = "rtwo";
                             break;
                         }
                     case 8: {
@@ -7853,18 +7857,22 @@ $root.jspb = (function() {
                         }
                     case 10: {
                             message.aone = reader.int32();
+                            message.defaultOneofA = "aone";
                             break;
                         }
                     case 11: {
                             message.atwo = reader.int32();
+                            message.defaultOneofA = "atwo";
                             break;
                         }
                     case 12: {
                             message.bone = reader.int32();
+                            message.defaultOneofB = "bone";
                             break;
                         }
                     case 13: {
                             message.btwo = reader.int32();
+                            message.defaultOneofB = "btwo";
                             break;
                         }
                     default:

Original file line number	Diff line number	Diff line change
`@@ -7827,18 +7827,22 @@ $root.jspb = (function() {`
`7827`	`7827`	`switch (tag >>> 3) {`
`7828`	`7828`	`case 3: {`
`7829`	`7829`	`message.pone = reader.string();`
	`7830`	`+ message.partialOneof = "pone";`
`7830`	`7831`	`break;`
`7831`	`7832`	`}`
`7832`	`7833`	`case 5: {`
`7833`	`7834`	`message.pthree = reader.string();`
	`7835`	`+ message.partialOneof = "pthree";`
`7834`	`7836`	`break;`
`7835`	`7837`	`}`
`7836`	`7838`	`case 6: {`
`7837`	`7839`	`message.rone = $root.jspb.test.TestMessageWithOneof.decode(reader, reader.uint32(), undefined, long + 1);`
	`7840`	`+ message.recursiveOneof = "rone";`
`7838`	`7841`	`break;`
`7839`	`7842`	`}`
`7840`	`7843`	`case 7: {`
`7841`	`7844`	`message.rtwo = reader.string();`
	`7845`	`+ message.recursiveOneof = "rtwo";`
`7842`	`7846`	`break;`
`7843`	`7847`	`}`
`7844`	`7848`	`case 8: {`
`@@ -7853,18 +7857,22 @@ $root.jspb = (function() {`
`7853`	`7857`	`}`
`7854`	`7858`	`case 10: {`
`7855`	`7859`	`message.aone = reader.int32();`
	`7860`	`+ message.defaultOneofA = "aone";`
`7856`	`7861`	`break;`
`7857`	`7862`	`}`
`7858`	`7863`	`case 11: {`
`7859`	`7864`	`message.atwo = reader.int32();`
	`7865`	`+ message.defaultOneofA = "atwo";`
`7860`	`7866`	`break;`
`7861`	`7867`	`}`
`7862`	`7868`	`case 12: {`
`7863`	`7869`	`message.bone = reader.int32();`
	`7870`	`+ message.defaultOneofB = "bone";`
`7864`	`7871`	`break;`
`7865`	`7872`	`}`
`7866`	`7873`	`case 13: {`
`7867`	`7874`	`message.btwo = reader.int32();`
	`7875`	`+ message.defaultOneofB = "btwo";`
`7868`	`7876`	`break;`
`7869`	`7877`	`}`
`7870`	`7878`	`default:`